/*
Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.


OJ's undirected graph serialization:
Nodes are labeled uniquely.

We use # as a separator for each node, and , as a separator for node label and each neighbor of the node.
As an example, consider the serialized graph {0,1,2#1,2#2,2}.

The graph has a total of three nodes, and therefore contains three parts as separated by #.

First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
Second node is labeled as 1. Connect node 1 to node 2.
Third node is labeled as 2. Connect node 2 to node 2 (itself), thus forming a self-cycle.
Visually, the graph looks like the following:

       1
      / \
     /   \
    0 --- 2
         / \
         \_/
*/

/**
 * Definition for undirected graph.
 * struct UndirectedGraphNode {
 *     int label;
 *     vector<UndirectedGraphNode *> neighbors;
 *     UndirectedGraphNode(int x) : label(x) {};
 * };
 */
class Solution {
public:
    UndirectedGraphNode *cloneGraph(UndirectedGraphNode *node) {
        if (!node) return node;
        queue<UndirectedGraphNode *> nqueue;
        unordered_map<UndirectedGraphNode *, UndirectedGraphNode *> nmap;
        UndirectedGraphNode *first = new UndirectedGraphNode(node->label);
        nqueue.push(node); nmap[node] = first;
        while (!nqueue.empty()) {
            UndirectedGraphNode *ori = nqueue.front();
            UndirectedGraphNode *clone = nmap[ori];
            for (auto it = (ori->neighbors).begin(); it != (ori->neighbors).end(); it++) {
                UndirectedGraphNode *cur = *it;
                if (nmap.find(cur) != nmap.end()) {
                    // neighbor already visited, add to neighbors list
                    clone->neighbors.push_back(nmap[cur]);
                } else {
                    UndirectedGraphNode *newnode = new UndirectedGraphNode(cur->label);
                    nmap[cur] = newnode; nqueue.push(cur); // enque to tail
                    clone->neighbors.push_back(newnode);
                }
            }
            nqueue.pop();
        }
        return first;
    }
};
